1. Field of the Invention
The invention relates to slip rings for transferring electrical power and/or signals between a rotating and a stationary part.
2. Description of Relevant Art
Electrical slip rings are used to transfer electrical power and/or signals between a rotating and a stationary part. Such devices are used in different applications, like wind energy plants or computer tomography scanners. There are also several military and aerospace applications. In all applications electrical current may be transferred continuously over a full rotation of the parts.
It is common to all of these applications, that a high lifetime and a low contact resistance as well as a low contact noise are required. Furthermore, in specific applications like a CT scanner, comparatively high speeds caused by a rotation of up to four revolutions per second in a circumference of about 5 meters require specific attention. The same applies for specific environmental requirements like in aerospace applications.
To increase lifetime, reliability, and to improve contact characteristics, it is known to lubricate a slip ring. The European patent publication EP 1 026 794 B1 discloses to lubricate a slip ring by using a lubricant with a selected viscosity. It is further noted therein that a certain amount of lubricant is required to ensure lubrication over a long service time, but application of too much lubricant should be avoided in order to prevent floating of the slip ring brush on the track.
The German Patent publication DE 10 2009 022959 B4 discloses a slip ring for a CT scanner which has a channel around the slip ring track to collect excess lubricant. Furthermore, a felt body is provided, redistributing the collected lubricant on the surface of the slip ring track.
In the European patent application publication EP 1 898 500 A2, a fiber brush slip ring is disclosed, which does not need any lubrication and therefore overcomes the above problems.